In the past, terrorist attacks on buildings have primarily involved the use of conventional weapons such as explosives, incendiary devices and firearms. Thus building defense systems presently in use are designed to protect against such conventional weapons and involve measures such as physical barriers, fire alarms, metal detectors, security checks and armed security personnel. The discovery of nuclear agents and the development of nuclear weapons and airborne chemical and biological contaminants and toxins has provided terrorists with sophisticated assault weapons against which present building defense measures are totally inadequate. An assault with a single or a combination of multiple hazardous airborne, waterborne or foodborne contaminants can occur with no perception of danger by the potential victims within a building. Such an assault can be particularly devastating when implemented by an aggressor from within the confines of a target building who is willing to sacrifice his or her life in the attack.
Systems for controlling the environment within a building have been developed which are responsive to combustion based pollutants in the outside air. Such systems, as illustrated by U.S. Pat. No. 5,462,485 to Kinkead, vary the amount of outside air drawn into a building in response to the concentration of a single pollutant in the outside air.
Additionally, a number of systems have been developed to provide conditioned air to a building interior in response to emergency conditions caused by smoke or harmful gasses. U.S. Pat. Nos. 4,380,187 and 5,720,659 to Wicks, 4,960,041 to Kiser and 5,215,499 to Eberhardt all disclose systems of this type.
None of the known prior art systems will effectively protect a building against an attack with airborne nuclear, biological or chemical contaminants from without or within the building. Furthermore, known systems are not capable of responding to different types of airborne contaminants used in combination.